I've been running for a while now, but this thing periodically drops to 42% GPU usage in a sharp microsecond spike. I shut down the client and went back to stock settings and it does the same thing. I think my overclock is stable.

This is most likely the client making sure that it saves your current progress. It's 100% normal.

What's up with the bad work units? I've had two of them now. On the last one I backed my clock way down because of erratic behavior, just to discover it was a bad work unit. Is this due to an unstable overclock?

Important (to me) discovery. This card has a switch for Normal, which it was on, OC mode and LN2 mode. After playing with it I've got it on LN2 at stock clocks, but folding at 1241mhz, 65c, and 1.184v. Folding has stabilized tremendously also. Have to wonder how much I can get out of this thing. Will definitely want to put it under water.

1241 is the best that my Lightning can do on air at this time of year, 1254-1267 depending on the unit during the winter. That's with a custom BIOS, adding some voltage, and a 80% fan at all times profile.

A custom BIOS is just that, 100% custom. That means that only your card will work with that BIOS, and nobody else's. Never use someone else's custom BIOS, that is basically you taking a 90% chance on killing your card willingly. I would not recommend making your own without a lot of research on how to do it.

A custom BIOS is just that, 100% custom. That means that only your card will work with that BIOS, and nobody else's. Never use someone else's custom BIOS, that is basically you taking a 90% chance on killing your card willingly. I would not recommend making your own without a lot of research on how to do it.

Sure don't want to brick my card. I'll just stick with what I've got. I need my water cooler! This thing puts out a lot of heat. Should have it with a decent case and new PSU by middle of the week. I'm running a 6-pin to 8-pin adapter on one leg. I do have a steady 11.94v though. It was a little over 12v until I turned this thing up to LN2.

I'll be patient. I pushed it to 1306 and it did well for about 8% of a 10472. Started erratic behavior, so I backed it off. Don't want to lose work units if I can help it. I would like to find the sweet spot like I did with my GTX-560 a few years ago. I folded 24/7 for months on that card at 999.9mhz. That was a killer card. I sold it to a kid who emails me on occasion bragging about the high settings he plays games in. Probably wasn't wise, but I left it overclocked and "hid" Afterburner. Still going strong as far as I know.